Calculation of Entropy Generation Rates via DSMC with Application to Continuum/Equilibrium Onset

Schrock, Christopher R.; McMullan, Richard J.; Camberos, José

doi:10.2514/6.2005-4830

Cited by 11 publications

(5 citation statements)

References 3 publications

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“…(Ideally we would consider the rate of change in vibrational entropy, ṡ v , but it can be shown that this rate is identically zero in an inviscid gas flow.) As given by Schrock et al for a simple gas, 19 ln…”

Section: B Comparison Of Measures For Vibrational Nonequilibriummentioning

confidence: 95%

Adaptive State Resolved Vibrational Energy Modeling for Hypersonic Flow Simulation

Burt

Josyula

2016

46th AIAA Thermophysics Conference

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Vibrational nonequilibrium is known to significantly influence flowfield and surface properties in a variety of hypersonic flows. Historical low fidelity CFD models for vibrational nonequilibrium, often based on a two-temperature approach, allow for efficient calculations at the cost of potentially large errors in computed output quantities. In contrast, high fidelity state resolved models are generally impractical for engineering analysis due to poor computational efficiency. While globally applied simplifications to full state resolved modeling routines have shown considerable potential for simple zero or one-dimensional flow problems, such simplifications have yet to be demonstrated as practical alternatives to a two-temperature approach for more complex flows of engineering interest. In this work, we explore the possibility of applying spatially adaptive approximations to a state resolved model, such that high fidelity modeling operations are performed only for vibrational levels and for flowfield regions where these operations are deemed necessary. Two different adaptive modeling techniques are proposed, and output quantity sensitivities are assessed for a simple inviscid flow of N 2 over a cylindrical forebody geometry. Excellent accuracy is found in translational and vibrational temperatures for sufficiently conservative choices of model input parameter values, although significant errors are consistently observed for upper vibrational levels within portions of the shock layer.

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Section: B Comparison Of Measures For Vibrational Nonequilibriummentioning

confidence: 95%

Adaptive State Resolved Vibrational Energy Modeling for Hypersonic Flow Simulation

Burt

Josyula

2016

46th AIAA Thermophysics Conference

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“…[4] that the entropy generation rate is likely to be one of the fundamental and most important parameters to predict the onset of non-equilibrium. Thermodynamic equilibrium is characterized by zero entropy generation, and non-equilibrium can be identified by positive entropy generation.…”

Section: Introductionmentioning

confidence: 99%

Entropy considerations in numerical simulations of non-equilibrium rarefied flows

Chigullapalli

Venkattraman

Иванов

et al. 2010

Journal of Computational Physics

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“…The approach did not provide significant benefits compared to the existing methods, as the calculations relied on data obtained from the continuum hypothesis. According to Schrock et al [11], substantial nonequilibrium could occur upstream of the normal shock. As a result, data based on the continuum hypothesis would not be able to capture the initial occurrence of the shock wave.…”

Section: Introductionmentioning

confidence: 99%

Feasibility of macroscopic parameters for NS to DSMC solver switching in micronozzle simulations

Kumar M,

Shine

2023

Phys. Scr.

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Enhancing the design and performance of micronozzles could lead to novel applications and advancements in propulsion systems, making the exploration of micronozzles crucial for the future. This paper critically examines the feasibility of utilizing macroscopic property-based Kn as indicator for defining the breakdown region during the transition from the NS solver to the DSMC solver in micronozzle simulations. The aim is to specify a parameter that can be calculated from both NS and DSMC simulations, making it suitable for implementation in hybrid simulations that dynamically switch between the two solvers. The results show that the density-based Kn accurately represents the continuum breakdown, and it exhibits an earlier breakdown compared to pressure and temperature-based Kn values. The study also analyzes the rarefaction effects and introduces the rarefaction parameter (RP), quantifying the increase in Kn for a unit change in the non-dimensionalized distance. The findings demonstrate that at very low exit pressures, the rarefaction effects increase rapidly as the flow moves towards the nozzle exit, leading to a transition from the continuum to the rarefied regime. The hybrid NS-DSMC simulations show good agreement with experimental data, validating the proposed approach. Additionally, the research examines the effect of back pressure on the RP and identifies the transition regime based on the slope of the RP curve. Therefore, the manuscript provides detailed insights into novel elements, such as the quantification of rarefaction within the nozzle using the RP, the classification of the nozzle into different regimes (continuum, slip, and transition), the definition of an easily obtainable parameter for switching between NS and DSMC methods, and an examination of the contributions of the shear stress term and heat addition term to non-equilibrium conditions.

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Calculation of Entropy Generation Rates via DSMC with Application to Continuum/Equilibrium Onset

Cited by 11 publications

References 3 publications

Adaptive State Resolved Vibrational Energy Modeling for Hypersonic Flow Simulation

Adaptive State Resolved Vibrational Energy Modeling for Hypersonic Flow Simulation

Entropy considerations in numerical simulations of non-equilibrium rarefied flows

Feasibility of macroscopic parameters for NS to DSMC solver switching in micronozzle simulations

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